/*

 * WebVTT subtitle encoder

 * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>

 * Copyright (c) 2014  Aman Gupta <ffmpeg@tmm1.net>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <stdarg.h>

#include "avcodec.h"

#include "libavutil/bprint.h"

#include "ass_split.h"

#include "ass.h"

#include "codec_internal.h"

#define WEBVTT_STACK_SIZE 64

typedef struct {

    AVCodecContext *avctx;

    ASSSplitContext *ass_ctx;

    AVBPrint buffer;

    unsigned timestamp_end;

    int count;

    char stack[WEBVTT_STACK_SIZE];

    int stack_ptr;

} WebVTTContext;

static av_printf_format(2, 3) void webvtt_print(WebVTTContext *s, const char *str, ...)

{

    va_list vargs;

    va_start(vargs, str);

    av_vbprintf(&s->buffer, str, vargs);

    va_end(vargs);

}

static int webvtt_stack_push(WebVTTContext *s, const char c)

{

    if (s->stack_ptr >= WEBVTT_STACK_SIZE)

        return -1;

    s->stack[s->stack_ptr++] = c;

    return 0;

}

static char webvtt_stack_pop(WebVTTContext *s)

{

    if (s->stack_ptr <= 0)

        return 0;

    return s->stack[--s->stack_ptr];

}

static int webvtt_stack_find(WebVTTContext *s, const char c)

{

    int i;

    for (i = s->stack_ptr-1; i >= 0; i--)

        if (s->stack[i] == c)

            break;

    return i;

}

static void webvtt_close_tag(WebVTTContext *s, char tag)

{

    webvtt_print(s, "</%c>", tag);

}

static void webvtt_stack_push_pop(WebVTTContext *s, const char c, int close)

{

    if (close) {

        int i = c ? webvtt_stack_find(s, c) : 0;

        if (i < 0)

            return;

        while (s->stack_ptr != i)

            webvtt_close_tag(s, webvtt_stack_pop(s));

    } else if (webvtt_stack_push(s, c) < 0)

        av_log(s->avctx, AV_LOG_ERROR, "tag stack overflow\n");

}

static void webvtt_style_apply(WebVTTContext *s, const char *style)

{

    ASSStyle *st = ff_ass_style_get(s->ass_ctx, style);

    if (st) {

        if (st->bold != ASS_DEFAULT_BOLD) {

            webvtt_print(s, "<b>");

            webvtt_stack_push(s, 'b');

        }

        if (st->italic != ASS_DEFAULT_ITALIC) {

            webvtt_print(s, "<i>");

            webvtt_stack_push(s, 'i');

        }

        if (st->underline != ASS_DEFAULT_UNDERLINE) {

            webvtt_print(s, "<u>");

            webvtt_stack_push(s, 'u');

        }

    }

}

static void webvtt_text_cb(void *priv, const char *text, int len)

{

    WebVTTContext *s = priv;

    av_bprint_append_data(&s->buffer, text, len);

}

static void webvtt_new_line_cb(void *priv, int forced)

{

    webvtt_print(priv, "\n");

}

static void webvtt_style_cb(void *priv, char style, int close)

{

    if (style == 's') // strikethrough unsupported

        return;

    webvtt_stack_push_pop(priv, style, close);

    if (!close)

        webvtt_print(priv, "<%c>", style);

}

static void webvtt_cancel_overrides_cb(void *priv, const char *style)

{

    webvtt_stack_push_pop(priv, 0, 1);

    webvtt_style_apply(priv, style);

}

static void webvtt_end_cb(void *priv)

{

    webvtt_stack_push_pop(priv, 0, 1);

}

static const ASSCodesCallbacks webvtt_callbacks = {

    .text             = webvtt_text_cb,

    .new_line         = webvtt_new_line_cb,

    .style            = webvtt_style_cb,

    .color            = NULL,

    .font_name        = NULL,

    .font_size        = NULL,

    .alignment        = NULL,

    .cancel_overrides = webvtt_cancel_overrides_cb,

    .move             = NULL,

    .end              = webvtt_end_cb,

};

static int webvtt_encode_frame(AVCodecContext *avctx,

                               unsigned char *buf, int bufsize, const AVSubtitle *sub)

{

    WebVTTContext *s = avctx->priv_data;

    ASSDialog *dialog;

    int i;

    av_bprint_init_for_buffer(&s->buffer, buf, bufsize);

    for (i=0; i<sub->num_rects; i++) {

        const char *ass = sub->rects[i]->ass;

        if (sub->rects[i]->type != SUBTITLE_ASS) {

            av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");

            return AVERROR(EINVAL);

        }

        dialog = ff_ass_split_dialog(s->ass_ctx, ass);

        if (!dialog)

            return AVERROR(ENOMEM);

        webvtt_style_apply(s, dialog->style);

        ff_ass_split_override_codes(&webvtt_callbacks, s, dialog->text);

        ff_ass_free_dialog(&dialog);

    }

    if (!s->buffer.len)

        return 0;

    if (!av_bprint_is_complete(&s->buffer)) {

        av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");

        return AVERROR_BUFFER_TOO_SMALL;

    }

    return s->buffer.len;

}

static int webvtt_encode_close(AVCodecContext *avctx)

{

    WebVTTContext *s = avctx->priv_data;

    ff_ass_split_free(s->ass_ctx);

    return 0;

}

static av_cold int webvtt_encode_init(AVCodecContext *avctx)

{

    WebVTTContext *s = avctx->priv_data;

    s->avctx = avctx;

    s->ass_ctx = ff_ass_split(avctx->subtitle_header);

    return s->ass_ctx ? 0 : AVERROR_INVALIDDATA;

}

const FFCodec ff_webvtt_encoder = {

    .p.name         = "webvtt",

    CODEC_LONG_NAME("WebVTT subtitle"),

    .p.type         = AVMEDIA_TYPE_SUBTITLE,

    .p.id           = AV_CODEC_ID_WEBVTT,

    .priv_data_size = sizeof(WebVTTContext),

    .init           = webvtt_encode_init,

    FF_CODEC_ENCODE_SUB_CB(webvtt_encode_frame),

    .close          = webvtt_encode_close,

};